Sound recording system



Dec. 14, 1937. CANADY 2,102,194

SOUND RECORDING SYSTEM Filed Sept. 3, 1936 oz U4;- H 3w U 9) Q A INVENTOR,

Jan 6'11 mad ATTORNEYS.

OUTPUT FROM AMPLIFIER Patented Dec. 14, 1937 titans- UNITED STATES PATENT OEFHQE Y SOUND RECORDING SYSTEM VDcn Canady, Cleveland, Ohio Application September 3, 1936, Serial No. 99,320

8 I Claims.

The generalobject of the present invention is to provide means to reduce the intensity of light reaching a film in recording sound thereby re-. ducing background noise when sound is being recorded on the photographic film.

It is also an object of my invention toprovide V intensity." V

It is also' an object of the invention a in: crease plate current of an evacuated tube so as to lower reactance of a s'aturable reactor.

It is also an object of the invention to increase plate current of an evacuatedtube thereby permitting increase of alternating current volt reactor associated therewith." V

It is also an object of the invention to regulate the intensity of light emitted by a recording lamp inproportion to the intensity of the signal entering the saturable reactor circuit.

Thebackgroundnoise is reduced according to my invention by means of saturable'reactor 'or reactors effected by a direct current fiowing'in a coil associated therewith which is connected to the plate of an evacuated tube. The increase of the plate. current lowers the reactance of the s'aturable reactor coils and permits an increase in the alternating currentyoltage through the reactor coils and the transformer associated therewithwhich in turn is connected in series with a rheostat and the primary of the said transformer 'age flowing through reactor coils of a saturable and the alternating current source of supply.

The system is primarily designed for increasing or decreasing the intensity of light reaching thesensitized surface of the film beyond the light source. Vibration of light, intensity on a. film may be compared to vibration of sound in air; To

record the sound of either instrumental or vocal music or both on a sensitized film surface requiresa variation of light intensity in the record- 1 l mp- V Y This system. overcomes most forms of back ground noises inrecording sound. It eliminates the most harmful noises to the ear or auditory system and produces a marked improvement in the sound recording. This system reproduces the range of sound in such a way, that the sound "thus recorded when reproduced may be heard with perfect clarity, volume and realism. The

. former 2.

the transformer I ll.

recorded sound is practically free from the distortion of background noise, so noticeable in recorded sound caused by the imperfectly controlled light vibration being transmitted to the sound recording film in recording.

It will beunderstood that the principle of my invention may be embodiedin various forms and that the details are not material. The present embodiment of the invention, therefore, is to be considered'as'merely indicative. The form i1lustrated in the drawing and hereinafter fully de-& scribed in detail has been found to be one of the practical embodiments'and capable of efficient operation in practical use and construction.

'Theinvention will be more clearly understood by reference to the: following specification and the accompanying drawing in which:--

The figure is a schematic wiring diagram of the system to reduce the intensity of light reaching the film.

As shown in the figure the coupling transformer l is connected tothe recording amplifier. Bridge across the primary of the coupling transformer l is the primary of the amplifying trans- The'secondary of the transformer l is connected to the recording lamp 3 in a conventional manner. The secondary of the transformer 3 feeds into the amplifier 4 the output of which is fed into another amplifying transformer 5. which in turn is electrically connected to the dry rectifier 6. The rectifier is shown as a dry rectifier but any suitable conventional rectifier may be used.

The rectified current from the dry rectifier 6 is fed to the vacuum tube 8 through the potentiometer land the battery M. The grid of the secondary of the transformer ill supplies alternating current voltage and current to the rectifier shown as a vacuum tube rectifier II to which is also connected another transformer [9 also connected to the alternating current source of supply. The rectified and filtered voltage from the rectifier l l supplies the recording lamp 3 through a conventional circuit. A rheostat i3 is provided to control the voltage to theprimary of The conventional circuit of the recording lamp is supplied with a plurality of filters It for filtering the current to the recording lamp 3. The film is shown at 20.

The operation of the apparatus is as follows:-

The reactance of the coils on the two outside legs of the saturable reactor 9 is effected by the direct current flowing in the center coil which is connected to the plate of the tube 8 and battery l6. An increase of plate current lowers the reactance and permits an increase in the alternating current voltage fiowing through the two outside coils of the saturable reactor and also in the primary of the transformer Ill to which it is connected in series and also to the alternating source of supply.

A signal comes from the recording amplifier to the lamp 3 and simultaneously to the amplifier 4. The signal is rectified by the rectifier 6 and applied to the vacuum. tube 8 through the potentiometer l and the battery l4. A positive potential is applied to the grid of the tube 8 in proportion to the intensity of the signal, the positive potential on the grid of the tube 8 increases the plate current of the grid 8, and flowing through the center leg of the saturable reactor, lowers the impedance permitting more alternating current voltage to reach the rectifier I l which in turn is applied to the recording lamp thus increasing the intensity of light following upon the film. The intensity of light emitted by the recording lamp is in proportion to the intensity of the signal entering the transformer 2.

With no signal entering the transformer 2, the grid of the vacum tube 8 becomes more negative and the plate current of the grid 8 drops increasing the reactance of saturable reactor 9,1owering the alternating current voltage at the secondary of the transformer II], which in turn lowers the voltage in the rectifier l I, the filter l 2 and the. recording lamp 3.

It is also to be understood that when there is a decrease in a signal in the signalling circuit, the potential on the grid is decreased thereby, causing a decrease in the plate current in the plate circuit, said decrease in the plate current causing a higher impedance in the reactor coils thereby permitting a decrease of the alternating current voltage to flow through the controlling circuit to the recording lamp in the amplifying circuit causing the said lamp to have a decrease in its light intensity.

In accordance with the provision of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus is only illustrative and that the invention may be carried out by other means. 7 i

What I claim and desire to secure by Letters Patent of the United States is:-

1. In an apparatus of the class described comprising an amplifying circuit, a secondary circuit electrically connected thereto and having therein a plurality of electrical translating means, one of which means has its plate circuit electrically associated with a leg of a saturable impedance positioned in an energy receiving circuit, the reactance of which reactor is partially controlled in the secondary circuit, a controlling circuit electrically associated with the energy receiving circuit and controlling the light intensity of the recording lamp in the amplifying circuit.

2. An automatic background noise controlling apparatus for controlling a light source in a recording lamp acting on a sound film, comprising an amplifying circuit, a translating circuit electrically associated with the amplifying circuit, a circuit comprising means for varying the light intensity in the recording lamp and having therein as a component thereof a saturable impedance which exerts automatic light controlling action in the recording lamp circuit thereby controlling the intensity of emergent light from the recording lamp thus permitting in the lamp variable illumination of the light intensity emitted in response to predetermined conditions, thereby avoiding optical imperfections of sound waves on the film that produce the background noises.

3. An apparatus of the class described comprising an amplifying circuit, a secondary signalling circuit electrically associated with the amplifying circuit, a vacuum tube plate circuit electrically connected to the secondary signalling circuit whereby positive potential on the grid of the vacuum tube is increased by an increase in a signal in the signalling current thereby causing an increase in the plate current in the plate circuit, means actuated by the said plate current causing the said means to have a lower impedance thereby permitting an increase of alternating current voltage to flow to a controlling circuit and thence to a recording lamp in the amplifying circuit causing an increase light intensity therein.

4. An apparatus of the class described comprising an amplifying circuit, a secondary signalling circuit electrically associated with the amplifying circuit, a vacuum tube circuit electrically connected to the secondary signalling circuit whereby positive potential on the grid of the vacuum tube is decreased by a decrease in a signal in the signalling circuit thereby causing a decrease in the plate current in the plate circuit, means actuated by the said plate current causing the said means to have a higher impedance thereby permitting a decrease of alternating current voltage to flow to a controlling circuit and thence to a recording lamp in the amplifying circuit causing a decrease of light intensity therein.

5. An apparatus of the class described comprising an amplifying circuit, a secondary signalling circuit electrically associated with the amplifying circuit, a vacuum tube plate circuit electrically connected to the secondary signalling circuit whereby the potential on the grid of the vacuum tube circuit becomes more negative when there is no signal entering from the signalling circuit thereby causing a drop in the plate current in the plate circuit, means actuated by the said plate current causing the said means to have an increase in its reactance thereby permitting a lowering of alternating current voltage to flow to the controlling circuit and thence to a recording lamp in the amplifying circuit causing a decrease of light intensity therein.

6. An apparatus for controlling light intensity to a recording lamp comprising an amplifying circuit; a translating circuit electrically associated therewith; a varying light intensity circuit electrically associated with the translating circuit and having therein as a component thereof a saturable impedance comprising a plurality of legs in spaced parallel relation and positioned in the path of the current between the translating circuit and a controlling circuit, the controlling circuit being electrically associated with the varying light circuit and the recording lamp instrumentality in the amplifying circuit.

7. An apparatus of the class described comprising an amplifying circuit, a translating circuit electrically associated with the aforesaid circuit, a light varying intensity circuit electrically associated with the translating circuit and having therein a fixed body component comprising a saturable impedance having longitudinally spaced legs, one of which is energized and controlled by means in the translating circuit in accordance with changes in the sound variations therein thereby controlling the light response indications in a recording light valve in the amplifying circuit.

8. In an apparatus of the character described comprising an amplifying circuit, a secondary circuit electrically connected thereto and having 15 therein a plurality of electrical translating means,

a component of which is a saturable impedance of predetermined configuration comprising a plurality of legs permanently united, some of the translating means in the secondary circuit being interconnected witha centrally disposed leg in the saturable impedance, the said impedance being disposed in the path of the secondary circuit, and a controlling circuit for controlling a I lamp instrumentality in the amplifying circuit whereby the light intensity in the recording instrumentality is controlled to permit maximlum response in accordance with changes in sound variations in all of the aforesaid circuits.

DON CANADY. 

